294 W. ARCHER. 



an outer cloudy protoplasmic envelope forming a matrix 

 whence radiate the spines, or in which lie imbedded the 

 spicules ; of this, however, more when the forms themselves 

 come to be referred to. 



The authors, however, point out as more important, that 

 the presence of spicules or spines is a widely enough 

 distributed characteristic in other groups ; thus in 

 Sponges, some Foraminifera — or of campanulate fenes- 

 trated siliceous tests, like the shells of Cyrtidse (as 

 pointed out by Hackel) in some pelagic Infusoria,^ 

 showing that resemblances of the skeleton may depend 

 as much on analogy as on homology, and therefore give no 

 ground for uniting two classes systematically, when the step 

 cannot be supported by characters based on the structure of 

 the soft parts. 



The authors, therefore, arrive at the conclusion that, in 

 the present state of our knowledge, there does not exist a 

 single characteristic in the structure of the Heliozoa which 

 would compel us to regard them as otherwise than remote 

 relations of the Eadiolaria. As yet the view that both 

 Classes have originated independently, and each for itself, 

 has the greater amount of evidence in its favour. But they 

 admit that a study of organization alone would not decide 

 the point, as only a comparative research into the develop- 

 ment-history of the two Classes would lead to a certain 

 decision. Unfortunately our knowledge as regards the latter, 

 in both instances, is very defective ; in the Heliozoa only en- 

 cysting — fission — zoospores — are known, whilst in Radiolaria 

 Cienkowski has described flagellate zoospores arising by 

 subdivision of the contents of the central capsule. Still 

 these observations, so far as they go, carry not much weight 

 as regards the question, for quite similar zoospores occur in 

 the Monothalamia,^ and, indeed, in Mycetozoa and in Cien- 

 kowski's " Monadince. Zoospores.'' 



But nothing is known of the mode whereby a zoospore, 

 in coming to rest, developes into a Radiolarian, and how out 

 of a probably unicellular structure a protoplasmic mass, in- 

 cluding many cell individuals, originates, and this knowledge 

 alone can inform us whether the Heliozoa bear a relation 

 to the Radiolaria comparable to that of lowly organized 

 forms to more highly developed. 



Hence the authors came to the above result; that is to 

 say, it is possible that an affinity between Radiolaria and 



* Hackel, "Ueber einige neue pelagische Infusorien," in 'Jenaische 

 Zeitsclirift,' Bd. vii, 4. 

 ' Hertwig, " Ueber Mikrogromia socialis," 1. c, p. 22. 



